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Arxiv_Daily_Notice/2026-05-01-Arxiv-Daily-Paper.md

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+# Showing new listings for Friday, 1 May 2026
+Auto update Star Formation & Molecular Cloud papers at about 2:30am UTC (10:30am Beijing time) every weekday.
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+
+阅读 `Usage.md`了解如何使用此repo实现个性化的Arxiv论文推送
+
+See `Usage.md` for instructions on how to personalize the repo. 
+
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+Keyword list: ['star formation', 'star-forming', 'molecular cloud', 'interstellar medium', 'cloud', 'clump', 'core', 'filament', 'atomic gas', 'N-PDF']
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+Excluded: ['galaxies', 'galaxy cluster', ' AGN ', 'standard candle', 'X-ray binar', 'solar corona']
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+
+### Today: 8papers 
+#### Beyond Cloud-9: The case for discovering more HI-rich failed halos
+ - **Authors:** Jorge Moreno, Coral Wheeler, Francisco J. Mercado, M. Katy Rodriguez Wimberly, Pratik J. Gandhi, Jenna Samuel, Robert Feldmann, James S. Bullock, Andrew Wetzel, Michael Boylan-Kolchin
+ - **Subjects:** Subjects:
+Astrophysics of Galaxies (astro-ph.GA)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27047
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27047
+
+ - **Abstract**
+ HI-rich starless halos, should they exist, hold great promise for elucidating properties of dark matter halos. This Letter examines the properties of HI-rich failed halos at redshift zero across state-of-the-art cosmological simulations (FIREbox, NIVARIA-LG and Recal-EAGLE). First we compare two numerical analogs with Cloud-9, purported to be the first discovery of a starless HI-rich halo. We argue that differences may be driven by environmental factors, and/or the treatment of gas self-shielding -- which might further limit existing analytic schemes aimed at inferring dark matter halo information from 21 cm HI observations. We also find that the failed halo samples in the three simulations span different regions of the HI-gas-halo mass ($M_{\rm HI}-M_{\rm gas}-M_{\rm 200}$) plane. FIREbox objects occupy a very narrow regime, while NIVARIA-LG extends to a wider range of $M_{\rm 200}$ values - and achieves higher $M_{\rm HI}$ and $M_{\rm gas}$ values. Recal-EAGLE $M_{\rm HI}$ values are similar to FIREbox, albeit with lower gas and halo masses. Lastly, we predict that more HI-rich starless halos can be discovered by exploring the HI-poor regime in the local universe, rather than HI-rich populations at high redshift. Overall, we advocate for the allocation of resources to detect and characterize other HI-rich (and HI-poor) failed halos in the local universe, plus dedicated follow-up spectroscopic observations that scrutinize claims to the absence of a faint stellar component, and that assess their isolation status in detail.
+#### SPYGLASS. VII-B. Tracing the Fragments of Massive Star Formation Using Low-Mass Associations
+ - **Authors:** Ronan Kerr, Adam L. Kraus, Jonathan C. Tan, Julio Chanamé, Facundo Pérez Paolino, Joshua S. Speagle, Juan P. Farias, José G. Fernández-Trincado, Keith Hawkins
+ - **Subjects:** Subjects:
+Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27067
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27067
+
+ - **Abstract**
+ New observations from the Gaia spacecraft have traced an emerging demographic of low-mass associations disconnected from larger associations or GMCs. The first of these associations were recently characterized, but the star-forming environments they trace remain unknown. Using new velocities and ages alongside literature catalogs, we uncover the origins of 16 low-mass associations ($M\lesssim100$ M$_{\odot}$, $\tau\lesssim50$ Myr) using dynamical traceback. We reveal that three groups of currently disparate populations share common formation sites, comprising the Leo, CaNMoS, and AquENS associations. Twelve of 16 associations have plausible connections to larger complexes, six of which form while moving outward from well-established multi-generational star-forming events that drive known or suspected bubbles. We find that feedback from the oldest co-spatial and co-moving relatives of these associations can explain the current morphologies of the Local and Orion-Eridanus Bubbles, along with the formation of related associations like Sco-Cen and Orion OB1. Most remaining populations show evidence for triggered star formation. In the Leo Association, high vertical velocities and a deceleration signature suggest that it formed out of an intermediate velocity cloud colliding with gas in Orion, which would make it the first known case of star formation in one of these clouds. The other newly defined associations show similar asymmetric velocity signatures, such as CaNMoS, which may trace bubble-driven acceleration or a cloud collision. We conclude that the lowest-mass young associations remain undiscovered, and that these populations may have a critical role revealing the small gas overdensities that trace the processes sculpting galactic star formation.
+#### Dust cloud lifetimes of Scallop-shell stars
+ - **Authors:** Simon Daley-Yates, Moira M. Jardine, Luke Bouma
+ - **Subjects:** Subjects:
+Solar and Stellar Astrophysics (astro-ph.SR)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27116
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27116
+
+ - **Abstract**
+ We investigate the survival of dust trapped in magnetically confined cool gas clouds (or {\it prominences}) around rapidly rotating M-dwarfs exhibiting the ``scallop-shell'' light-curve morphology. Using a two-dimensional magnetohydrodynamic simulation, we extend previous coronal prominence models to include a passive tracer field to allow for a single injection of collisionally charged dust grains. The tracer evolution reveals how recurrent centrifugal breakouts--the slingshot process--remove dust and gas from the prominence while chromospheric evaporation replenishes gas from below. For our simulated star, which has $R_{\ast} = 0.6 R_{\odot}$, $M_{\ast} = 0.3 M_{\odot}$, and $P_{\ast} = 0.32$ days, the resulting dust content decays exponentially with a minimum half-life of approximately 6 stellar rotations, representing a lower limit set by our assumption of fully coupled dust and gas dynamics. Synthetic velocity-phase diagnostics show a single, phase-locked feature that fades steadily, reproducing the behaviour of dips seen in TESS and K2 light curves. Comparison with observed river plots suggests a natural classification: (i) persistent, non-decaying features formed by quiescent prominences below co-rotation; (ii) gradually fading features produced by slingshot prominences near co-rotation; and (iii) abrupt disappearances linked to magnetic reconnection and flare-driven ejections. These results demonstrate that dust-bearing prominences--undergoing repeated slingshots--can persist for tens of rotations, linking the observed longevity of the scallop-shell photometric features with the dynamic cycle of prominence slingshot ejections.
+#### Star cluster formation from turbulent clumps. V. Stellar clustering around massive stars
+ - **Authors:** Aayush Gautam, Juan P. Farias, Jonathan C. Tan
+ - **Subjects:** Subjects:
+Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27382
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27382
+
+ - **Abstract**
+ Massive stars (> 8 $M_\odot$) are known to have high degrees of multiplicity, e.g., with about 60% in triples or higher-order multiples. Such high levels of multiplicity may arise during formation (primary multiplicity) or through dynamical processing of already formed stars in dense clusters (secondary multiplicity). The level of primary multiplicity is an important metric to help distinguish between different formation scenarios, such as core accretion and competitive accretion. The level of secondary multiplicity is expected to evolve with time and be sensitive to local cluster environment. Here we analyze a suite of $N$-body simulations to study bound multiplicity and local projected stellar density, $N_*$, around massive stars within gradually forming star clusters with 50% primordial binaries in the Turbulent Clump Core Accretion (TCCA) paradigm. We find that massive stars rapidly gather triple or higher-order bound companions and enhancements in local $N_*$ via dynamical processes. We study these metrics as a function of environment in a given cluster, quantifying the increasing multiplicity that arises towards cluster centers. We find that secondary multiplicity tends to decrease in more massive clusters due to their higher velocity dispersions, but rises as the mean density of the bound cluster increases. We find our $N_*$ radial profiles are shallower compared to those in the STARFORGE simulations, which form massive stars via competitive accretion. A comparison to the AFGL 5180 system suggests it is better described by TCCA models. However, a larger number of observed systems is needed to better discriminate between these formation models.
+#### Dense cores and filaments in M16: Enhanced formation efficiency in the stellar feedback-driven shell
+ - **Authors:** Nageen Pervaiz, Guo-Yin Zhang, Alexander Men'shchikov, Jin-Zeng Li
+ - **Subjects:** Subjects:
+Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27584
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27584
+
+ - **Abstract**
+ We present a comprehensive analysis of dense cores and filamentary structures in the M16 Eagle Nebula using high-resolution ($11.7^{\prime\prime}$) surface density and temperature maps derived from \textit{Herschel} observations. Using the \textit{hires} algorithm for map construction and the \textit{getsf} method for source and filament extraction, we identified 233 cores and 111 filaments in this massive star-forming region. The filaments exhibit a median width of 0.4\,pc -- and a median linear density of 61\,$M_\odot$\,pc$^{-1}$, with 76\% being supercritical for gravitational fragmentation. Our radial analysis of the $\sim$60\,pc diameter shell driven by the central NGC 6611 cluster reveals strong enhancements in structure formation: filament formation efficiency (FFE) is 2.3 times higher within the shell (peaking at 22\%), while core density shows a concurrent 1.5-fold enhancement. The moderate correlation between core density and FFE ($r=0.67$) indicates coupled formation processes. Theoretical analysis demonstrates that observed surface densities exceed the critical threshold for fragmentation by a factor of $\sim$8, with a fragmentation timescale ($\sim$1.5--2.0\,Myr) comparable to the shell's dynamical age ($\sim$1.0--1.3\,Myr), indicating we are observing fragmentation in progress. These results reveal a hierarchical fragmentation sequence -- shell compression $\rightarrow$ filament formation $\rightarrow$ core formation -- providing clear observational evidence for positive feedback where massive star formation triggers secondary structure formation in the surrounding molecular cloud.
+#### Radio signal generation in milliseconds: enabling multi-parameter reconstruction of ultra-high-energy cosmic rays
+ - **Authors:** Arsène Ferrière (for the GRAND Collaboration)
+ - **Subjects:** Subjects:
+Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)
+ - **Arxiv link:** https://arxiv.org/abs/2604.27684
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.27684
+
+ - **Abstract**
+ In recent years, radio detection of ultra-high-energy cosmic rays (UHECRs), with energies above $10^{18}$ eV, has become an established technique. The radio emissions can be simulated with high accuracy using Monte Carlo codes such as ZHAireS and CoREAS. These simulations are essential but are computationally intensive. In this work, we present a machine-learning-based emulator that reproduces radio signal simulations with high accuracy in milliseconds rather than hours. Primary particle properties can then be reconstructed by comparing measured signals to emulated traces using a Markov Chain Monte Carlo approach. Using ZHAireS simulations carried out over the GRANDProto300 experiment layout, the method achieves an 8.9\% resolution on electromagnetic energy and a 0.08° angular resolution, matching state-of-the-art reconstruction performance. Finally, we apply the method on real data, successfully reconstructing cosmic-ray candidates detected by the GP300 prototype.
+#### The Influences of Hydrogen-Silicate-Iron Miscibility on the Demographics of Sub-Neptunes and Super-Earths
+ - **Authors:** Edward D. Young, Aaron Werlen
+ - **Subjects:** Subjects:
+Earth and Planetary Astrophysics (astro-ph.EP)
+ - **Arxiv link:** https://arxiv.org/abs/2604.28135
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.28135
+
+ - **Abstract**
+ Models based on variable miscibility among hydrogen, molten silicate, and molten iron, coupled with atmospheric escape, can reproduce the observed occurrence density structure of sub-Neptunes and super-Earths in mass-radius space. The models are also consistent with the radius gap and the observed radius-period relationship exhibited by these planets. The degree of overlap between predicted and observed planetary occurrences suggests that hydrogen-silicate-iron miscibility may serve as a unifying concept for the formation and evolution of these planet classes. The well-defined equilibrium conditions at the boundary between supercritical magma oceans and the overlying hydrogen-rich envelopes are important features of the models. Planets formed with less than ~1 % hydrogen by mass develop discrete, terrestrial-like metallic cores, while those accreting greater hydrogen concentrations are predicted to have fully miscible interiors and no discrete metal cores. Hydrogen-silicate-iron miscibility provides an overarching explanation for the full range of sub-Neptune and super-Earth architectures based on the accreted hydrogen mass fraction and the phase equilibria governing silicate, iron metal, and H$_2$ miscibility.
+#### Chemical Taxonomy of $ω$~Centauri: Ten Populations Reveal a Multi-Phase Enrichment History
+ - **Authors:** Furkan Akbaba, Olcay Plevne, Timur Şahin, Sena Aleyna Şentürk
+ - **Subjects:** Subjects:
+Astrophysics of Galaxies (astro-ph.GA)
+ - **Arxiv link:** https://arxiv.org/abs/2604.28195
+
+ - **Pdf link:** https://arxiv.org/pdf/2604.28195
+
+ - **Abstract**
+ $\omega$~Centauri, the most massive globular cluster in the Milky Way, exhibits a level of stellar population complexity that has long resisted a unified chemical characterisation. We exploit high-resolution near-infrared spectroscopy from the Milky Way Mapper survey (MWM DR19) to construct one of the largest homogeneously analysed samples of $\omega$~Cen members to date. Applying Ward-linkage hierarchical clustering in a seven-dimensional chemical abundance space, without prior assumptions on population number or boundaries, we identify ten chemically distinct stellar populations. Their nucleosynthetic signatures trace four enrichment channels: iron-peak, $\alpha$-element, CNO-cycle, and high-temperature proton-capture processes. The populations organise into two dominant groups separated by a large light-element spread at a modest iron baseline, consistent with AGB-driven self-enrichment. This dichotomy reflects distinct enrichment pathways: core-collapse supernovae establish the iron baseline, while AGB stars dominate light-element and $s$-process enrichment. A decoupled rise in $s$-process abundances relative to iron-peak elements, together with sub-dominant Type~Ia contributions across all metallicities, indicates evolution on timescales shorter than the characteristic Type~Ia delay time. One intermediate-metallicity population retains a primordial composition, providing evidence for spatially segregated enrichment within the progenitor. The most metal-rich component may trace star formation continuing after accretion into the Milky Way halo. All populations lie in the accreted regime of the $[\mathrm{Al/Fe}]$--$[\mathrm{Mg/Mn}]$ plane, supporting an ex-situ origin. These results reinforce the interpretation of $\omega$~Cen as the remnant nucleus of an accreted dwarf galaxy and provide a framework for future chemo-dynamical studies.
+
+
+by olozhika (Xing Yuchen). 
+
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+2026-05-01